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Researchers link feedback loops, ecosystems

Team explores pivotal role of feedback loops in maintaining diverse ecosystems

Merging physics and environmental science, an interdisciplinary team including a University researcher recently published a paper examining how feedback loops influence ecosystem changes.

The paper, published online March 30 in the journal Trends in Ecology and Evolution, discusses how feedback loops — cycles that output information that is put back into the starting point — interact in forests and savannahs in relation to the alternative stable-state theory. This theory contends that feedback reinforces ecosystems and that the loss of a feedback loop can result in ecosystem change.

“The core of the climate model is all based on physics,” said Brad Marston, professor of physics and co-author of the paper. Climate models depend on temperature, fluid dynamics and radiation, all of which can be modeled using concepts from physics, he said.

Another lesson from physics is that “complex systems can react in unexpected ways,” Marston said. The climate is one such complex system.

In the paper, the researchers use forests and savannahs as two examples of ecosystems that are maintained by feedback loops, and in which the loss of feedback loops effects change.

Forests retain water, reducing the likelihood of fires, increasing nutrients in the soil and thus reinforcing the ecosystem. On the other hand, savannah grasslands are more flammable, increasing the likelihood of fires, decreasing nutrients in the soil and thus reinforcing the ecosystem.

“You can reach a tipping point from forest to savannah and it’s hard to get back,” Marston said.

Disruption of these two feedback loops can lead to the destruction of both forest and savannah ecosystems. For example, in forest ecosystems, high rates of tree damage and loss can threaten the feedback loop, raising the risk of deforestation, Marston said.

One example of a feedback loop that has led to environmental disruption involves climate change. Climate change involves ecosystems becoming drier and trees releasing more carbon dioxide, which in turn leads to greater climate change, Marston said.

The alternative stable-state theory is more generally applicable to the consequences of climate change, Marston said.

Deforestation occurred in the past in the Mediterranean and could occur in other places in the future, he said.

In addition to the factors the researchers identified, topography and elevation can also be significant factors in landscape changes, said Steven Archer, professor at the School of Natural Resources at the University of Arizona, who was not involved in the study.

In North America, south-facing slopes receive more radiation and are warmer and drier, allowing for more rapid changes in the environment, Archer said.

Marston collaborated with David Bowman, professor of environmental change biology at the University of Tasmania and George Perry, associate professor at the School of Environment at the University of Auckland.


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